Dual ratio lever mechanism



ly 1 1959 E. R. FRYER 2,893,13

DUAL RATIO LEVER MECHANISM Filed April so, 1956 2 Sheets-Sheet 1 INVENTORS Eda/074 2?? A TTOR/VE Y July 7, 1959 E. R. FRYER DUAL RATIO LEVER MECHANISM 2 Sheets-Sheet 2 Filed April 30, 1956 ATTORNEY United States Patent DUAL RATIO LEVER MECHANISM Edward R. Fryer, Euclid, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application April 30, 1956, Serial No. 581,719

Claims. (Cl. 37-118) Thisinvention relates to earth handling vehicles and more particularly, although not exclusively, to an improved mechanism for raising the bowl apron of such vehicles.

Self-propelled bowl type scrapers are conventionally equipped with a front apron which may be raised to facilitate ejection of earth or other material carried in the bowl. Because of the position of the apron relative to the load mass, initial displacement of the apron requires the application of a great force. However, after the apron has been raised partially, a substantially redu ced force is effective to displace the apron through its remaining increment of movement. In the past many bowl apron lift mechanisms have obtained the requisite initialforce at the expense of optimum apron elevation. In other cases, satisfactory initial lifting force and optimum apron travel has been accomplished by employing lift cylinders of excessively large capacity.

An object of the present invention is to provide an improved bowl apron lift mechanism.

Another object is to provide an apron lift mechanism capable of imparting adequate initial lift force and optimum apron travel.

'A further object is to provide an apron lift mechanism of the type described which may be operated by a hydraulic lift cylinder of relatively small capacity.

Still a further object is to provide a lever type apron lift mechanism which is eifective initially to produce a high lift force and a subsequent greatly increased bowl apron travel.

Yet a further object is to provide a double articulated bowl apron lift mechanism.

A still further object is to provide an apron lift mechanism in which a hydraulic cylinder assembly is arranged to react against a lever assembly in such a way that initial reaction-of the cylinder assembly causes the lever assembly to swing about a primary fulcrum providing relatively great mechanical advantage and further reaction of the cylinder assembly causes the lever to swing about a secondary fulcrum providing reduced mechanical advantage and increased travel. a

Still another object is to provide in a device of the type described an articulated lever structure which is so arranged that the free end thereof initially fulcrums about an axis providing one radius of movement and subsequently about a second axis on the lever providing greatly decreased radius of movement.

Still a further object is to provide a device of the type described including a sheave assembly connecting the free end of the lever with the bowl apron.

These and other objects, advantages and features of the invention will become more fully apparent as reference is bad to the accompanying specification and drawings wherein:

Fig. l is a view illustrating a portion of a typical earth moving scraper and showing the location and relative arrangement of parts of the invention when the bowl apron is in the closed carrying position; and

2,893,139 Patented July 7, 1959 Fig. 2 is a view similar to Fig. 1 showing the relative relationship of the parts when the bowl apron is in the open or ejection position.

In the drawings, the reference numeral 2 designates generally the gooseneck portion 2 of the scraper bowl pull yoke 4. At its forward end, not shown, portion 2 is adapted for connection to a draft vehicle, not shown. At its rearward end gooseneck 2 is rigidly connected to a transverse hexagonal beam 6 which, in turn, has connected at opposite ends thereof a pair of rearwardly extending booms 8. It will be understood that the second boom 8 extends rearwardly from the opposite end of hexagonal beam 6 in parallel relation with the boom illustrated. At their rearward ends, booms 8 are pivotally connected on a common axis at 10 intermediately on the side walls 12 of bowl 14. Suitable bowl elevatiing mechanism, not shown, is arranged to react between gooseneckl and the forward end of bowl 14 in order to regulate the elevation of the transverse cutting edge 16 near the forward end of the bowl bottom wall 18. Since the bowl elevating mechanism forms no part of the invention, further description will be omitted, it being understood that any conventional type may be employed. Disposed transversely across the open front 20 of bowl 14 is a transversely extending bowl apron 22. Apron 22 is curved in cross section to correspond with the curvature of the curved front configuration of bowl 14. At its upper end apron 22 is connected rigidly to a pair of spaced apart rearwardly extending arms 24. Arms 24 straddle the opposite side walls 12 of bowl 14 and are pivotally connected thereto on a common axis 26. Axis 26 is located to provide upward swinging movement of apron 22 through an are generally corresponding with the arcuate profile of the front of bowl 14.

In order to accomplish raising of apron 22 in accordance with the present invention, the forward end of a double articulated lever assembly 28 is pivotally connected at 30 on the rearwardly facing wall 32 of a transverse support 34 mounted intermediately on gooseneck 2. Assembly 28 comprises a primary lever 36 and a secondary lever 38 which are pivotally connected together at 40. Lever 38 is generally U-shaped in cross section and is provided with a top wall portion 42 which has mounted on the undersurface thereof an abutment portion 44. Portion 44 normally serves to engage the forward upper surface 46 of the extremity 48 of lever 36 to resist clockwise swinging movement thereof. Near its rearward end, the top wall 42 of lever 38 merges with an inclined end wall 50 which is adapted to abut a stop 52 on support 34 after predetermined counterclockwise movement of lever 38. Rearwardly of pivot pin 40, pri mary lever 36 is pivotally connected at 53 to the upper open end of a piston rod 54 of hydraulic cylinder assembly 56. Cylinder 58 of assembly 56 is, in turn, pivotally connected at 60 to the lower extremity 62 of gooseneck 2. At its rearward extremity, primary lever 36 is provided with a cable sheave 64 which is rotatable about a transversely extending trunnion 66 carried by lever 36. An apron lift cable 68 extends around sheave 64 and is connected at one end 70 to gooseneck 2 and at the opposite end 72 to the lower wall 74 of apron 22.

In order that the invention may be more fully understood, a description of the sequence of operation follows: Assume that the bowl 14 is fully loaded with earth or other material and it is now desired to raise the apron to permit ejection of the material therefrom. Through a suitable hydraulic pressure supply system, not shown, the operator introduces hydraulic fluid under pressure into the cavity 76 of cylinder assembly 56. Fluid pressure in assembly 56 causes piston 54 to exert a lifting force on lever assembly 28. Since the weight of apron 22 and the bowl oifer resistance to upward movement of sheave 64, continued pressure at 53 on lever assembly 28 causes the rearward extremity 48 of primary lever 36. .to react against the abutment pad .44 .ofsecondary .lever- 36. Therefore, both the primary and secondary levers fulcrum about pivot axis 30.. Because of the dis- .tance between pivot 30 and, the, reaction .point 53 of piston 5.4,v high initial mechanical advantage is applied to thereafter prevents further angular movement of the secondary lever. Consequently, continued. displacement of piston 54; requires that primary lever36 fulcrum about pivot 40 atthe, rearward end of secondary lever 38. Since the fulcrum provided by pivot 40 is much nearer the. reaction point 53 than the original fulcrum at 30, the rate of angular movement of sheave 64 increases substantially without any increase in the displacement rate of piston 54. In addition, the angular distance traveled by sheave 64relative to the total linear distance traveled by piston 54 is greatly increased. Therefore, after the initial breakaway action of apron 22, when maximum lifting effort is no o g eq d, the f mech m m. is effe tive t provide both rapid elevation andan optimum level of elevation of the apron.

From the foregoing it will be seen that a novel and efficient bowl apron. lift mechanism has been devised. The structure is not only simple in construction and operation, but also permits substantial reduction in cost by allowing the use of a relatively small capacity cylinder assembly without any loss in efiiciency. The invention has the further advantage of providing optimum lifting effort when resistance to movement of the apron is greatest and subsequently providing greatly improved apron speed and degree of elevation when maximum lifting force is; no longer required.

'while but one embodiment of the invention has been shown and described, it will be apparent. that other changes and modifications may be made therein. It is, therefore, to be understood that it is not intended to limit the invention to the embodiments shown but only by the scope of the claims which follow.

What is claimed is:

l. A dual ratio lever assembly comprising a first lever pivotally mounted at one end on a support, a second lever pivotally mounted on the other end of said first lever, means on said support limiting angular movement of said first lever in one direction only, means on said second lever limiting angular movement thereof in the opposite direction relative to said first lever, means on the free end of said second lever connected to a load, and force applying means arranged to react between said support and said second lever.

2. A lever assembly comprising a first lever pivotally mounted on a support, a second lever pivotally connected to-said first lever, means on said support limiting angular movement of said first lever in one direction, means on said second lever limiting angular movement thereof in the opposite direction relative to said first lever, and force applying means mounted on said support and arranged to. react against said second lever at a point spaced between the pivotal connection of said first and second levers and the. free end of said second lever.

3. A lifting mechanism comprising'a first lever pivotally mounted on a support, a second lever pivotally mounted. on said first lever, means. on said support providing a predetermined limit of angular movement for saidv first lever in one direction, means on said second lever limiting angular movement thereof in the opposite direction relative to said first lever, force applying means arranged. to react between said support and said second lever at a point spaced between the pivotal. connection of said first and second levers and the free end of said second lever, and load engaging means mounted on the free end of said second lever.

4. A dual ratio lift mechanism comprising a support, a pair of pivotally connected levers, interengaging means on said levers normally aligning the latter in a common plane preventing clockwise movement of one lever relative to the other, means pivotally connectingthe other lever to said support, an abutment on said support engageable with a portion of said other lever after predetermined counterclockwise movement thereof, force exerting means disposed between said support and said one lever, and means for connecting the free end of said last mentioned lever to a load whereby upon application of force said pair of levers initially function as a single lever swinging in a counterclockwise direction until said other lever reaches said predetermined angular position whereupon saidlonelever continues to swing in a counterclockwise direction about the pivotal connection between said levers.

5. In a lever assembly having one end pivotally connected to a support and the other end connected to a load, stop means on said support limiting angular movement; of; said leverin one direction about said pivotal connection, means for obtaining hig initial lifting force nda sub quent ift ng orce of lesser magn udebut P viding greater-rate and distance of travel than said initial atwo part lever, .a hinge connecting said parts toprevent relative angular movement therebetween in one direction, means pivotally connecting one of said parts to said support, means on said last mentioned part adapted to abut .said support after predetermined angular movement in a direction opposite to said first mentioned direction, means for exerting a force on the other part, and means connecting the free end of said other part to a load whereby the application of force initially causes both of said parts to function as a single lever until said one part reaches said predetermined angle, whereupon said second part functions independently as a lever pivoting about said hinge.

7. In an earth working machine of the type including a load carrying bowl, the combination of a pull yoke connected to said bowl, a closure member hinged on .said bowl and movable to permit discharge of the contents of said bowl, and means for raising said closure member comprising a two part lever pivotally mounted at one end on said pull yoke, means on the other end of said lever engaging said closure member, a thrust producing device disposed between said pull yoke and said lever, means on said two part lever adapted to provide high mechanical advantage during predetermined initial angular movement of, said lever and subsequently a reduced mechanical advantage but an increased range of movement for the free end of said lever, said means comprising a hinge connecting said two parts, and a stop on said pull'yoke adapted to disable the lever action of one part of said lever after predetermined angular movement thereof.

8. In an earth working machine of the type having a material carrying bowl provided with a hinged apron normally closing a portion of said bowl, a dual ratio lever assembly for raising said apron comprising a support, a first lever pivotally mounted on said support, a second-lever pivotally mounted onsaid first lever, means on said support providing a predetermined limit of angu- 5 6 lar movement for saidfirst lever in one direction, means 10. The structure set forth in claim 8 wherein said jack on said second lever hmitlng angular movement of said comprises an expansible fl id moton second lever in the opposite direction relative to said first lever, a jack arranged to react between said sup- References Cited in the file of this patent port and said second lever at an intermediate point, and 5 means for connecting the free end of said second lever UNHFED STATES PATENTS to said apron. 673,036 m r Apr. 30, 1901 9. The structure set forth in claim 8 wherein said 1,5 ,619 Fife! Nov. 25, 1924 means connecting the free end of said second lever with 2,773,320 Fryer et a1. Dec. 11, 1956 said apron comprises a sheave rotatably mounted on said 10 lever and a cable surrounding said sheave and having its FORFTIGN PATENTS opposite ends connected respectively to said support and 165,075 Austria-11a Sept. 7, 1955 said apron. 

